Tungsten Copper Electrode Manufacturing

Except liquid-phase sintering, infiltration and direct sintering, there are some new technologies of tungsten copper come out recently, which make the structure and micro-structure of tungsten copper more stable.

1. Rapid directional solidification

Based on good thermal and electric conductivity, rapid solidification remarkably improves the strength and erosion resistance of tungsten copper electrode at high temperature. However, the cooling rate of rapid solidification is still lower so that solidification structure has sufficient time to grow up and coarsening, which may cause severe support segregation and decrease the properties of tungsten copper.

Given concern such situation, it need to improve the cooling rate by increasing the gradient temperature of the solid-liquid interface in the process of solidification. There are many kinds of rapid directional solidifications, such as SDS (Supercooling Directional Solidification), laser rapid directional solidification with ultra-high temperature gradient and electromagnetic shaping directional solidification.

2. In-situ reactions

Tungsten copper electrode always adopts passive pressure infiltration casting, but it has an unavoidable disadvantage that tungsten skeleton will be oxidized, which decreases the associativity of matrix and the properties of product. In the process of in-situ reactions, enhanced phase is forming in metal liquid and do not expose in the air so that it is isolated from outside and the properties will be improved. The process is that mix tungsten and copper powder (WO3 and CuO), and sinter in the air after forming (CuWO₄), then reduce in H₂. Finally, put the blank into copper solution. The relative density of tungsten copper composite material can reach 99% in such this way.

3. FGM (Functional Gradient Material)

W-Cu composite material is kind of new material that tungsten copper composite layer is between Cu and W. It can apparently relax the heat stress by mismatch between tungsten and copper properties. There are two techniques for FGM, one is that discontinuous gradient layer, such as traditional powder piling, which has faults among each layer, the other is that continuous gradient layer, such as slip casting, settle casting, centrifugal casting, which takes advantage of natural transfer to forming continuous contents.

 To some extent, FGM sintering is similar to traditional PM (Powder Metallurgy) process, which can be specifically divided into solid-phase sintering, liquid-phase sintering and dipping sintering. In addition, some processes adopt non-sintering method, such as plasma coating, laser-cladding, electrophoresis deposition and centrifugal casting.